Approximately 1.5 billion people worldwide suffer from chronic pain of various etiologies. Pain is a leading cause of combat injured soldiers' and veterans' disability. Acute and chronic pain afflicts military personnel and veterans in proportions far exceeding those of the general population. A limited cohort study of Operation Enduring Freedom or Operation Iraqi Freedom veterans found 81.5% experienced chronic pain. Almost 30% of all veterans seek healthcare treatment for persistent chronic pain.
Currently, opioids, such as morphine, are the cornerstone of pain management in veterans suffering from chronic pain due to severe injuries (polytrauma), post-traumatic stress disorder (PTSD) and traumatic brain injury (TBI) or post-concussive syndrome. However, therapeutic administration of morphine often does not result in adequate, long lasting attenuation of chronic pain, as well as produces a number of deleterious side effects including respiratory depression, sedation, constipation, nausea, vomiting, addiction, tolerance, and increased suicide risks. Prescribed opioids (e.g., μ-opioid receptor agonists) have become some of the most highly abused drugs as measured by treatment center admission/cause of overdose; abuse of prescription drugs by the military is more than twice that seen in the civilian population—11% compared to 5%, according to a 2008 military survey. Alternative non-opioid based pain therapies are urgently needed. A deeper understanding of the complexity of pain mechanisms will lead to more rational and targeted approaches to pain therapies and to safer and more effective pain treatments.